beta
I looked it up on amazon.co.jp. There are only 4 compiled volumes out so far. Vol 4 has 5 chapters (ch17-ch21), two sides ("Kuroji and Harutsugu" & "Tsugumi's maid"), and an afterword.
It appears that Megumi & Tsugumi is still ongoing as of the QPa v143 release in Nov 2023, containing chapter 30. So it's going to be at least 6 volumes if not more...